Characterization of diffractive bifocal intraocular lenses.

Multifocal intraocular lenses incorporate a variety of design considerations, including dimensioning of the base monofocal shape and the diffraction grating. While studying three different lens models, we present a practical approach for mathematical modelling and evaluation of these geometries. Contrary to typical lens measurement methods, non-contact measurements were performed on the Alcon SN6AD1, HumanOptics MS 612 DAY and the AMO ZMA00 lenses using a confocal microscope. Subsequent data processing includes centering, tilting correction, filtering and an algorithmic decomposition into a conic and polynomial part and the diffraction grating. Lastly, evaluation of fitting parameters and grating shape is done to allow for inferences about further optical properties. Results and analysis show the confocal microscope to be a suitable imaging method for lens measurements. The processing of this data enables the reconstruction of the annular diffraction grating over the complete lens diameter. Apodization, near addition and diffraction efficiency characteristics are found utilizing the grating shape. Additionally, near-optical axis curvature, asphericity and higher order polynomials are identified qualitatively from the reconstruction of the monofocal base form. Derived properties also include the lens optical base and addition power. By making use of the surface geometries, as well as the lens' material and thickness, a full lens model can be created for further studies. In summary, our analytical approach enables the insight to various intraocular lens design decisions. Furthermore, this procedure is suitable for lens model creation for research and simulation.

Clear Cornea Femto DALK: a novel technique for performing deep anterior lamellar keratoplasty.

PURPOSE: A new femtosecond laser assisted deep anterior lamellar keratoplasty technique (Clear Cornea Femto DALK or CCF DALK) can be performed with less technical challenges compared to conventional procedures. This paper reports on a preliminary case series to evaluate the technique. METHOD: First, through a clear cornea approach, Descemet's membrane (DM) is completely separated from posterior stroma by injection of balanced salt solution/viscoelastic substance through a special cannula inserted into the deep stroma and positioned right above the DM without perforating. The injection creates a liquid chamber that detaches the DM while preserving a reasonably transparent corneal stroma. Afterwards, a complete posterior/anterior trephination of the stroma, from the liquid chamber to the epithelium, is done using a femtosecond laser system under optical coherence tomography control. RESULTS: This technique was successfully performed in a preliminary series of 10 eyes/10 patients. All patients had the DM completely bared and kept their own endothelial cell population with minimal cell loss (< 15%) after 6 months. Postoperative interface reaction was minimal, and no immune reactions were observed thus far. CONCLUSION: Clear Cornea Femto DALK is a promising alternative to previous Femto DALK procedures with good acceptance of the tissue seen to date.

Treating capsule contraction syndrome with a femtosecond laser.

We describe a technique that uses a femtosecond laser (femtosecond laser pseudophakic capsulotomy) to treat capsule contraction syndrome (capsule phimosis) that may occur after cataract surgery and intraocular lens (IOL) implantation. Enlarging the capsulotomy with a femtosecond laser may offer advantages over the existing treatment methods, neodymium:YAG laser capsulotomy and manual extension of the capsulorhexis. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Comparability of an image-guided system with other instruments in measuring corneal keratometry and astigmatism.

PURPOSE: To test whether keratometry (K) and astigmatism measurements provided by the Verion Reference Unit (an image-guided system) compared well with the Tonoref II automated tonometer-refractometer, IOLMaster partial coherence interferometry (PCI) biometer, AL-Scan optical biometer, Pentacam rotating Scheimpflug camera, and OPD Scan III wavefront aberrometer. SETTING: Augenklinik am Neumarkt, Cologne, Germany. DESIGN: Retrospective case series. METHODS: Patients having routine cataract surgery had standard preoperative assessment including biometry measurement with all study devices. The K values, power of astigmatism, axis, and the lens power of an imaginary intraocular lens (IOL) were analyzed for each device. RESULTS: One hundred five eyes of 62 patients with a mean age of 68.5 years ± 11.9 (SD) (range 27.2 to 89.7 years) were included in the study. The mean differences in flat K readings between the image-guided system and the tonometer-refractometer, PCI biometer, optical biometer (2.4 and 3.2 mm), rotating Scheimpflug camera, and wavefront aberrometer were -0.03 mm, 0.00 mm, 0.01 mm (both 2.4 and 3.2 mm), -0.03 mm, and -0.01 mm, respectively (P < .001). Differences were slightly greater for steep K readings as follows: -0.04 mm, -0.01 mm, -0.02 (optical biometer 2.4 mm), -0.03 mm (optical biometer 3.2 mm), -0.04 mm, and -0.06 mm, respectively (P < .001). The calculated power of an imaginary IOL from the study devices fell within 0.28 diopter of one another (P > .05). CONCLUSIONS: The image-guided system compared well with and provided astigmatism measurements similar to those of currently available diagnostic measurement devices. This system can aid appropriate preoperative IOL power calculations. FINANCIAL DISCLOSURES: Drs. Schultz, Oberheide, and Kermani have received honoraria from Alcon Pharma GmbH for corporate presentations.

Rotation stability of the cachet angle-supported phakic intraocular lens.

PURPOSE: To evaluate the rotational stability of an acrylic angle-supported phakic intraocular lens (PIOL) 12 months after implantation in myopic eyes. METHODS: Patients with a history of moderate to high myopia underwent unilateral or bilateral implantation of an acrylic angle-supported PIOL (AcrySof Cachet; Alcon Laboratories, Inc., Fort Worth, TX). All were followed up for 12 months. IOL rotation was assessed using digital overlay of ocular photographs captured within 2 weeks of implantation and at postoperative month 12. The secondary outcomes of refractive power (spherical equivalent, refractive sphere, and cylinder) and uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were assessed preoperatively and again at 3 months after implantation. RESULTS: Fifty eyes of 28 patients with a mean age of 32 years were included in this retrospective cohort study. All underwent successful IOL implantation and follow-up. A mean 12-month rotation of 11° was observed (standard deviation: 15.1°, range: 0 to 60°). All preoperative measures (mean) of refractive power improved by 3 months postoperatively (spherical equivalent = -0.35 ± 0.79 diopters [D], spherical refraction = 0.04 ± 0.82 D, and cylindrical refraction = -0.77 ± 0.91 D). Two percent of eyes requiring additional laser adjustment by postoperative month 12, primarily due to corneal astigmatism. CONCLUSION: The study findings suggest that AcrySof Cachet angle-supported PIOLs offer moderate 1-year rotational stability. Because this type of IOL also corrects myopia effectively, it appears to be a good treatment option for myopic eyes. However, the rotation that occurs makes it unsuitable for cylinder corrections.

Femtosecond lentotomy: generating gliding planes inside the crystalline lens to regain accommodation ability.

Based on Helmholtz Theory for accommodation the increasing sclerosis of lens nucleus and cortex is the main cause for the developments of presbyopia. Existing therapies, however, do not reverse the stiffness of the crystalline lens and thus do not regain real accommodation ability. A new approach to restore the flexibility of the lens could be realized by photodisruption using ultrafast laser pulses. This process, known as fs-lentotomy, was used to create micro-incisions which act as gliding planes inside the crystalline lens without opening the eye globe.

Control of femtosecond thin-flap LASIK using OCT in human donor eyes.

PURPOSE: Thin-flap keratomileusis is a procedure that minimizes LASIK flap thickness to preserve both the corneal epithelium and the maximum residual stroma. This study investigated the usefulness of optical coherence tomography (OCT) as a tool in guiding the femtosecond laser in the creation of a thin flap in human eyes in a non-randomized case series. METHODS: In a private research laboratory, an in vitro investigation was performed on human autopsy eyes. Five human cadaver eyes, unsuitable for transplantation, underwent flap creation with a femtosecond laser. The laser procedure was controlled in real-time with an OCT system (Thorlabs HL AG) to ensure that the cut was placed just underneath Bowman's layer. The repetition rate of the femtosecond laser was 10 MHz with a single-pulse duration of <400 femtoseconds (pulse energy in the nJ range). As a control, all eyes underwent histological dissection and were examined using light microscopy. RESULTS: Video monitoring of the flap creation supported the feasibility of real-time OCT monitoring of the femtosecond laser flap creation process. A clear distinction of the corneal epithelium was possible in all eyes. Bowman's layer was not identified in all donor eyes at the given resolution of the OCT device used in this study. Light microscopy demonstrated flaps approximately 50-microm thick, confirming that the real-time monitoring assured a positioning of the cutting plane at minimum distance underneath Bowman's layer. CONCLUSIONS: This study of five human cadaver eyes shows that real-time OCT monitoring of the creation of thin-flaps in LASIK using a femtosecond laser is possible, thus ensuring that the flap is created at the desired depth.

Dual intraocular lens implantation: Monofocal lens in the bag and additional diffractive multifocal lens in the sulcus.

PURPOSE: To evaluate a new diffractive multifocal intraocular lens (IOL) as an additional (add-on) IOL for sulcus-based implantation. SETTING: Augenklinik am Neumarkt, Köln, Germany. METHODS: In this prospective study, cataract patients had phacoemulsification and IOL implantation. After phacoemulsification, an aspheric silicone monofocal IOL (MS 612 ASP-Y) with a power range of +4.00 to +27.00 diopters [D]) was implanted in the capsular bag. This was followed by sulcus placement of an add-on multifocal IOL (MS 714 PB) with a +3.50 D diffractive element for near but zero refractive power for distance. RESULTS: The study included 56 eyes of 30 patients. Three months postoperatively, the mean monocular uncorrected distance visual acuity was 0.10 logMAR +/- 0.11 (SD) (median 1.00 decimal; 20/20 Snellen), with a remaining mean postoperative spherical equivalent of 0.01 +/- 0.51 D. The mean uncorrected intermediate visual acuity was 0.20 +/- 0.15 logMAR (median 0.63 decimal; 20/30 Snellen) with a luminance of 500 lux at 1 m. The mean uncorrected near visual acuity (Early Treatment Diabetic Retinopathy chart) was 0.16 +/- 0.13 logMAR (median 0.80 decimal; Jaeger 2). No major complications (eg, iris chafing, iris capture, lens epithelial cell ingrowth, glaucoma) were associated with the add-on IOL in the sulcus. CONCLUSIONS: Combined implantation of an add-on diffractive sulcus IOL and a monofocal capsular bag IOL was safe and effective in improving far and near visual acuity in cataract surgery. Preliminary visual acuity results were similar to those in eyes with a single 1-piece diffractive multifocal IOL.

Femtosecond laser induced flexibility change of human donor lenses.

BACKGROUND: According to the Helmholtz theory of accommodation the loss of accommodation amplitude is caused by the growing sclerosis of the crystalline lens, whereas the ciliary muscle and the lens capsule are mainly uneffected by age. A permanent treatment method for presbyopia which offers a dynamic accommodation ability is a recent field of study. The concept followed in this paper uses femtosecond laser pulses to potentially overcome the loss of deformation ability of the crystalline lens by creating gliding planes inside the lens tissue to improve its flexibility. METHODS: The aim of the study is to show that the flexibility of human donor lenses can be increased by applying tightly focused near infrared femtosecond laser pulses into the lens tissue. Thereby the tissue is separated by the photodisruption effect. A certain pattern of gliding planes is cut inside the tissue of 41 human donor lenses and the deformation ability of the lenses are compared using the Fisher spinning test before and after laser treatment. RESULTS: The laser treatment results in an increased deformation ability of the crystalline lens. The lens a-p thickness increases on average by 97 microm+/-14 microm after the treatment. The Fisher spinning test shows an increase of 16% in deformation ability of the lens at a rotational speed of 1620 rpm. CONCLUSION: The creation of gliding planes with a fs laser inside the crystalline lens tissue can change the deformation ability of the lens. This might be an indication for a possible method to treat presbyopia in future.

Outcomes of hyperopic LASIK with the NIDEK NAVEX platform centered on the visual axis or line of sight.

PURPOSE: To report refractive outcomes of hyperopic LASIK with automated centration on the visual axis compared with centration on the line of sight (LOS). METHODS: The NIDEK Advanced Vision Excimer Laser platform (NAVEX) was used to treat 181 hyperopic eyes with centration on the LOS (LOS group) and 64 hyperopic eyes with centration on the visual axis (visual axis group). The coordinates of the visual axis were digitally transferred to the excimer laser system based on the positional relationship between the LOS and the coaxially sighted corneal light reflex. All eyes were treated with a 6.5-mm optical zone and 9.0-mm transition zone. Three-month postoperative outcomes were retrospectively analyzed. RESULTS: The preoperative manifest refraction spherical equivalent (MRSE) was +2.57+/-1.26 diopters (D) (range: 0.13 to 5.63 D) in the visual axis group and +2.46+/-1.32 D (range: 0.38 to 5.63 D) in the LOS group. The postoperative MRSE was +0.29+/-0.70 D (range: -1.00 to 1.75 D) in the visual axis group and +0.19+/-0.57 D (range: -0.75 to 1.75 D) in the LOS group. Postoperatively, 81% (38/47) of eyes in the visual axis group and 64% (74/116) of eyes in the LOS group were +/-0.50 D. In the visual axis group, 91% (44/52) of eyes and 92% (102/109) of eyes in the LOS group maintained best spectacle-corrected visual acuity within one line compared with preoperatively. CONCLUSIONS: Initial experience with hyperopic LASIK centered on the visual axis indicated safe and predictable outcomes.

In vivo application and imaging of intralenticular femtosecond laser pulses for the restoration of accommodation.

PURPOSE: According to the Helmholtz theory of accommodation, one major cause of the development of presbyopia is the increasing sclerosis of the crystalline lens. One concept for regaining the elasticity of the sclerosing lens is intralenticular treatment by femtosecond laser pulses. METHODS: The feasibility of applying and imaging in vivo microincisions by femtosecond laser pulses was evaluated in five rabbit lenses with a new high repetition rate (100 kHz) femtosecond laser unit. The treated eyes were monitored using optical coherence tomography (OCT) and Scheimpflug imaging for localizing and studying the tissue effects of the incisions. The rabbits were investigated preoperatively, immediately postoperatively, and 14 days after treatment. RESULTS: The procedure, termed femtosecond-lentotomy, was successfully applied to the left lens of each rabbit. The laser microincisions within the crystalline lens were detectable with OCT and Scheimpflug imaging, which emphasizes the integral role these technologies play in targeting and characterizing postoperative tissue effects. The imaging within the lens showed a progressive fading of the incisional opacities generated by the femtosecond laser after 14 days with no detectable cataract formation. CONCLUSIONS: It is possible to create microincisions inside the crystalline lens within an acceptably short treatment time (<30 seconds). The 14-day follow-up did not show undesirable side effects, such as cataract formation, after intralenticular laser treatment.

Comparative micromorphologic in vitro porcine study of IntraLase and Femto LDV femtosecond lasers.

PURPOSE: To assess flap creation and stromal bed quality of 2 femtosecond refractive surgery lasers in laser in situ keratomileusis. SETTING: Augenklinik am Neumarkt, Cologne, Germany. METHODS: Corneal flaps were created in 115 freshly enucleated porcine eyes using the 60 kHz IntraLase FS laser (Advanced Medical Optics) and a prototype model of the Femto LDV femtosecond laser (Ziemer Ophthalmic Systems AG). The parameters that were evaluated included actual versus intended thickness by subtraction pachymetry, cutting and total suction time, quality of flap edges, and smoothness of flap beds. Confocal microscopy (Atos PLmu [Altos GmbH]) was used to objectively determine the root mean square (RMS) of the surface roughness of the stromal bed. RESULTS: Cutting time was 31 seconds for the 60 kHz IntraLase FS laser and 38 seconds for the Femto LDV laser. With both lasers, the standard deviation in achieved versus intended flap thickness was small (136 microm +/- 10 and 130 +/- 9 microm, respectively). Under micromorphologic examination, stromal bed quality was slightly better with the IntraLase. The RMS of bed roughness was 1.6 +/- 0.5 microm with the IntraLase and 2.0 +/- 0.4 microm with the Femto LDV. Neither laser showed significant thermal or mechanical damage in adjacent tissue layers of the stromal bed. The laser-induced bubble layer was more pronounced with the IntraLase. CONCLUSION: The laser cuts of the IntraLase FS and Femto LDV femtosecond lasers were equally smooth and of excellent quality. The standard deviation of the flap thickness was small and equal in both systems.

fs-Laser induced elasticity changes to improve presbyopic lens accommodation.

BACKGROUND: According to the Helmholtz theory of accommodation, one of the major reasons for the development of presbyopia is the progressive sclerosis of the crystalline lens. However, both the ciliary muscle and the lens capsule stay active and elastic. Thus, the concept for regaining the deformation-ability of the crystalline lens is to create microincisions inside lens tissue to achieve gliding planes. METHODS: For the preparation of the microincisions, near-infrared femtosecond laser pulses are used, generating laser-induced optical breakdowns. Different cutting patterns were performed, and the elasticity regain of the lenses were measured with Fisher's spinning test for thickness determination. RESULTS: The creation of gliding planes inside lens tissue shows very good results in terms of increasing the deformation-ability. The optimization of laser parameters leads to a minimally invasive surgery with no remarkable side effects like residual gas bubbles. Furthermore, ex vivo elasticity measurements of untreated and treated pig lenses show an improvement in the flexibility of the lens. The deformation-ability increases up to 26% with a very low standard deviation (1.6%) and a high significance (p < 0.05). CONCLUSION: Generating particular cutting patterns inside lens tissue can increase the deformation-ability of the crystalline lens. Thus, it might be one possible way to treat presbyopia.

Topographic- and wavefront-guided customized ablations with the NIDEK-EC5000CXII in LASIK for myopia.

PURPOSE: To assess refractive outcomes, changes in the total higher order root mean square (RMS) aberration, and changes in higher order wavefront aberrations after LASIK for myopia and myopic astigmatism with the NIDEK Advanced Vision Excimer Laser platform (NAVEX) using either an aspheric or topography-based or whole eye wavefront ablation algorithm. METHODS: This was a retrospective study of 1459 eyes that underwent LASIK for myopia and myopic astigmatism. The mean preoperative spherical equivalent refraction was -4.68 diopters (D) (range: -0.50 to -9.63 D) with astigmatism up to -4.50 D. Treatments were classified into three categories depending on the type of ablation algorithm used--optimized aspheric transition zone (OATz) denoted eyes that underwent aspheric treatment zones; customized aspheric treatment zone (CATz) denoted eyes that underwent customized ablations based on corneal topography; and OPDCAT denoted eyes that underwent customized ablation based on the whole eye wavefront profile. Follow-up data are reported at 3 months (69%) and 12 months (17%) postoperatively. RESULTS: Three months after LASIK, the predictability (10.5 D from target refraction) was 80% for OATz, 91% for CATz, and 76% for OPDCAT. Of all eyes, 96% were within +/- 1.0 D of intended refraction 3 months postoperatively and 100% after 12 months (87% +/- 0.5 D). In the aspheric and custom groups, a notable improvement of uncorrected visual acuity was noted between 3 and 12 months after LASIK. No eye lost >1 line of best spectacle-corrected visual acuity. Mean higher order RMS increased in all groups. CONCLUSIONS: The data support that the treatment of myopia and myopic astigmatism is safe and effective with NAVEX. Customized ablation based on corneal topography rather than on total wavefront error was more predictable.

Hyperopic laser in situ keratomileusis with 5.5-, 6.5-, and 7.0-mm optical zones.

PURPOSE: To evaluate the results of laser in situ keratomileusis (LASIK) for the correction of hyperopia and hyperopic astigmatism using a large 7.0-mm optical zone and to compare them with treatments using a 5.5- and 6.5-mm optical zone. METHODS: One hundred sixty-one eyes of 89 patients with a mean preoperative spherical equivalent refraction of +2.44 +/- 1.32 diopters (D) (range: +0.00 to +5.62 D, cylinder 5.25 to 0.00 D) were treated for hyperopia and hyperopic astigmatism using a 7.0-mm optical zone and were analyzed retrospectively. Postoperatively, patients were examined after 1 day, 1 week, 1 month, 3 months, and 1 year. Eyes treated previously at the same center by the same surgeons with 5.5- and 6.5-mm optical zone applications were used as controls. All treatments were performed with the Nidek EC 5000 CXII excimer laser system (Nidek, Gamagori, Japan). A nasal hinged flap was created using the Nidek MK 2000 microkeratome in all cases. RESULTS: The mean postoperative spherical equivalent refraction after 1 month (n=89) was +0.12 +/- 0.72 D (range: -1.75 to +2.75 D), +0.13 +/- 0.74 D (range: -1.88 to +1.62 D) at 3 months (n=70), and +0.20 +/- 0.69 D (range: -1.62 to +1.12 D) at 1 year (n=33). Regression between 1 month and 1 year was 0.08 D in the 7.0-mm optical zone group. Regression was 0.25 D in the 5.5-mm group and 0.02 D in the 6.5-mm optical zone group between 1 month and 1 year. In both the 5.5- and 6.5-mm optical zone groups, 13% of eyes lost one line in visual acuity (2% in the 7.0-mm optical zone group). The gain of one or more lines in visual acuity was 19% in the 5.5-mm group, 17% in the 6.5-mm group, and 27% in the 7.0-mm optical zone group. All data represent primary cases without retreatment. CONCLUSIONS: Increasing the optical zone size from 5.5 mm to 6.5 mm and to 7.0 mm seems to improve refractive results, stability, and safety of hyperopic and hyperopic-astigmatic LASIK treatments. Although some hyperopic and astigmatic eyes are endangered by loss of lines in best spectacle-corrected visual acuity, more eyes gain one or more lines.

Early results of nidek customized aspheric transition zones (CATz) in laser in situ keratomileusis.

PURPOSE: Standard ablation profiles for myopia and myopic astigmatism are spherical in shape and usually induce spherical aberration, often resulting in glare, halo, and other night vision problems. New ablation algorithms with aspheric transition zones may help reduce the amount of induced spherical aberrations in refractive surgery. METHODS: Between September and November 2002, 52 eyes were treated with bilateral laser in situ keratomileusis (LASIK) using a new ablation profile with customized aspherical transition zone (CATz). Results were analyzed from examinations performed 1 day, 1 and 3 months (if available) after surgery, and compared to a standard LASIK patient group. RESULTS: Refractive outcome of patients was within +/- 0.50 D of intended correction in 72% on day 1, and 82% at 1 month after surgery. At 1 month after LASIK, mean spherical equivalent refraction was changed from preoperative mean -6.73 +/- 2.04 D to postoperative mean -0.43 +/- 0.80 D (range -2.00 to +1.50 D). No eye lost more than 1 line of visual acuity; 10% gained 1 line and 80% remained unchanged 1 month after surgery. The topographically visible effective optical zone size was larger than in comparable treatments with standard ablation profiles. Spherical aberration was reduced and no patient complained about night vision problems after surgery. CONCLUSIONS: Customized aspheric transition zones may help reduce induction of spherical aberration in refractive surgical correction of myopia and myopic astigmatism.

Optoacoustic imaging for optimization of laser cyclophotocoagulation.

Optoacoustic imaging was used for ophthalmic imaging, especially of the ciliary body region, which is of interest in the treatment of glaucoma. The different tissue structures below the sclera of porcine and rabbit eyes in vitro could be differentiated up to a depth of more than 1.5 mm. Based on the optoacoustic signals, two-dimensional tomographic images could be generated for visualization of this region in a B-scan mode. In addition, changes during the coagulation process could be measured in real time, allowing the development of online control mechanisms for cyclophotocoagulation, which is an important therapy of glaucoma.